Re: [TUHS] [SPAM] Re: If not Linux, then what?

[Larry McVoy <lm@mcvoy.com>]

I could be wrong but that's my memory.  What he told me was streams was
for line disciplines for tty drivers.  That's what I know but you were
there, I was not.  I'm pretty confused because what Dennis said to me
was that he did not think streams would work for networking, he thought
they made sense for a stream but not for a networking connection because
that had multiple connections coming up through a stream.

I'm happy to be wrong but can you talk more about what he was thinking?
There is no way that I'm saying you are wrong, you are you, I just want
to learn.  If there is a way that streams made sense for networking I'd
like to see that.  My experience with STREAMS is that they sucked really
hard for networking.  

My guess is I need to go learn about mpx, I don't know that.

On Wed, Aug 28, 2019 at 01:22:33PM +1000, Rob Pike wrote:
> I find it hard to believe what you remember Dennis saying. The point of
> dmr's streams was to support networking research in the lab and avoid the
> myriad bugs of the mpx interface by stepping around them completely.
> 
> Perhaps it's out of context.
> 
> -rob
> 
> 
> On Wed, Aug 28, 2019 at 9:00 AM Larry McVoy <lm@mcvoy.com> wrote:
> 
> > streams were OK but Dennis himself told me he didn't intend them for
> > networking.  They were a simple mechanism for pushing line disciplines
> > onto tty drivers.
> >
> > I can't remember exactly what he said, this was back in ~1988 or so
> > and I was talking to him about the STREAMS stuff.  He wasn't very
> > happy with it and I'm pretty sure he said something like streams
> > weren't design to mux multiple sources or network connections.
> > I think he sort of grudgingly gave credit that they made it work
> > but he seemed to think that it was twisting streams more than they
> > should be twisted.
> >
> > On Wed, Aug 28, 2019 at 08:46:35AM +1000, George Michaelson wrote:
> > > oh maybe I meant "streams" not "STREAMS" I always got confused if the
> > > original ritchie spec was upper or lower case. Charles Forsyth coded
> > > it into the York Uni Vaxen, worked fine. I left shortly after to do
> > > stuff at UCL, it only came back into my life when at UQ in Australia
> > > we got an ICL "certified" SYSV host and along side dead technology
> > > like RFS up it popped (I think ICL had coded an OSI stack we were
> > > testing)
> > >
> > > -G
> > >
> > > On Wed, Aug 28, 2019 at 8:40 AM Larry McVoy <lm@mcvoy.com> wrote:
> > > >
> > > > Wait, are you arguing for STREAMS over sockets?  Dear god, please no.
> > > > Have you ever used STREAMS (not Ritchies streams, those were OK)?
> > > > I have.  I ported Lachman's STREAMS based TCP/IP stack twice, once
> > > > to a long since defunct super computer called the ETA-10 and then
> > > > to SCO Unix.  I've got way more STREAMS experience than most people
> > > > and I can tell you that sockets are WAY WAY better.  I get the "it
> > > > should have just been file I/O" except that I don't.  I tried to
> > > > write a library that let you open up /net/tcp/$host:$port and do
> > > > I/O like it was a file descriptor.  That works for a lot of stuff
> > > > but I ran into problems quickly.  A networking connection is not
> > > > a file handle.  You can make some stuff work but I couldn't figure
> > > > out how to do all of it.   You end up having to do ioctls to handle
> > > > the stuff that doesn't fit well into the file system name space.
> > > > I think plan 9 did this sort of thing, maybe Rob can prove me wrong
> > > > or remember where it didn't match.
> > > >
> > > > I do know that STREAMS came back to Solaris, some VP inked a shitty
> > > > deal with Lachman and bought the rights to the stack.  It was slow
> > > > as molasses in the winter and customers absolutely hated it.  Sun
> > > > got Mentat to redo it for perf but customers still hated it, they
> > > > understood sockets, everyone else had sockets, they wanted sockets
> > > > and they got them.  Sun put them back and nobody ever asked about
> > > > STREAMS again.
> > > >
> > > > On Wed, Aug 28, 2019 at 08:30:01AM +1000, George Michaelson wrote:
> > > > > BSD, but with the original STREAMS semantics, not sockets.
> > > > >
> > > > > DARPA did us no favours accepting sockets in place of simple file I/O
> > > > > semantics for networks.
> > > > >
> > > > > Newcastle connection put the namespace into
> > > > > /.../remote-part/path/to/thing which I felt was also good.
> > > > >
> > > > > So for me, 7 -> BSD -> got worse for some values of worse
> > > > >
> > > > > On Wed, Aug 28, 2019 at 12:56 AM Larry McVoy <lm@mcvoy.com> wrote:
> > > > > >
> > > > > > On Mon, Aug 26, 2019 at 11:14:45PM -0400, Arthur Krewat wrote:
> > > > > > > On 8/26/2019 10:45 PM, Larry McVoy wrote:
> > > > > > > >  Which was that the page cache is
> > > > > > > >*the*  cache.  There is nothing else.
> > > > > > > Yeah, I re-read what you wrote a few times after I replied, and
> > realized
> > > > > > > what you meant ... eventually ;)
> > > > > >
> > > > > > I might be making too big of a deal about it.  mmap semantics
> > mattered
> > > > > > a lot when SMPs first showed up and main memory was small.  It
> > meant
> > > > > > that you could have multiple CPUs seeing and working on the same
> > chunk
> > > > > > of data at the same time.
> > > > > >
> > > > > > It's very similar to way that IOMMUs are exposed to user space
> > these
> > > > > > days, enabling virtual machines direct access to the I/O devices.
> > > > > >
> > > > > > ZFS breaks that model, the data is all in the ARC and if you mmap
> > > > > > it they have to bcopy the data out of the ARC, into the page cache
> > > > > > and now they have a consistency problem, you could modify stuff
> > > > > > via mmap or write and they have to manage that.
> > > > > >
> > > > > > That consistency problem is the main reason that Sun almost
> > completely
> > > > > > killed the buffer cache (it still was used for inodes and
> > directories
> > > > > > but that was it).  That consistency problem is a pain in the rear,
> > > > > > all sorts of race conditions and it tended to bit rot.
> > > > > >
> > > > > > Jeff and Bill are smart people so I suspect they got it right but
> > I'm
> > > > > > still stunned that they took such an architecturally bad approach.
> > > > > > And even more stunned that the oversight people approved it.  There
> > > > > > is zero chance that the Sun I worked at would have allowed that.
> > > > > >
> > > > > > --lm
> > > >
> > > > --
> > > > ---
> > > > Larry McVoy                  lm at mcvoy.com
> > http://www.mcvoy.com/lm
> >
> > --
> > ---
> > Larry McVoy                  lm at mcvoy.com
> > http://www.mcvoy.com/lm
> >

-- 
---
Larry McVoy            	     lm at mcvoy.com             http://www.mcvoy.com/lm